1. GENETICS The Science of Heredity Mrs. Brunner Science 7 th Grade

2. I. Gregor Mendel  A. Mendel’s Pea Experiments - 1851 1. Monastic monk 2. While growing peas, he noticed purebred plants… 3. He cross pollinated purebred plants tall peas with purebred short peas and got… 4. parent generation = P generation, filial = F 1 5. big idea – a. pairs of factors control inherited traits(1male, 1female) b. genes c. 1 allele is dominant, 1 is recessive d. dominate allele always ‘masks’ the recessive allele

3. 6. hybrid – 7. What happens when plants have… a. 2 dominant alleles for tall stems… b. 1 dominant allele for tall, 1 recessive for short stems... C. 2 recessive alleles for short stems…  B. Symbols used 1. parent generation – 2. filial – 3. dominant allele – upper case 4. recessive allele – lower case http://www.promotega.org/UGA06003/genetic_crosses.htm http://www2.edc.org/weblabs/WebLabDirectory1.html

4. II. Probability and Genetics  A. Probability – likelihood that a certain event will occur, events are independent of each other  B. Mendel was first to figure out…  C. Punnett Squares 1. chart that shows all possible outcomes of genetic cross, each possible combination of alleles 2. predicts genetic possibilities 3. make sure you can read a Punnett Square! If unsure, check pgs. 90-91

5. PUNNETT SQUARES http://users.adelphia.net/~lubehawk/BioHELP!/psquare.htm http://users.adelphia.net/~lubehawk/BioHELP!/psquare.htm

6.  D. Phenotypes and Genotypes 1. phenotype – physical appearance, trait, ex…. 2. genotype – genetic makeup, allele combination, ex…. a. homozygous alleles – both alleles are the same, TT b. heterozygous alleles – alleles are different, Tt  E. Codominance 1. some alleles are not dominant or recessive 2. both alleles are expressed in offspring 3. codominant alleles are are written with a superscript, for example…go to pg. 93

7.  F. Meiosis 1. 1903, Walter Sutton… 2. sex cells – specialized cells that join together to form a new organism, 3. they only have ½ the number of chromosomes so that when they join together… 4. meiosis – process by which the number of chromosomes is reduced by ½ to form sex cells 5. similar to mitosis b/c chromosomes copy, line up on spindle fibers, form new cells and separate 6. different to mitosis b/c there are 2 divisions that result in only ½ the number of chromosomes 7. what/where is a gene?